Flow through applicators have become a well accepted part of dentistry. Such applicators are usually operatively affixed to a source of liquid or gel material. The source usually has means for pressurizing the liquid-gel into and through the applicator. In many instances the source may be a loaded syringe On the other hand the source may be the applicator itself which may have a proximate chamber for containing a liquid. The chamber is fitted with a piston plug for driving the liquid out of the applicator.
In many instances the distal end of the applicator is fitted with bristles so that the liquid or gel flowing from the applicator can be distributed as by brushing back and forth for instance. Such bristles frequently overlap the bore out of which the liquid or gel is being expressed and thereby hinders the clear flow capability.
When no bristles are present the end of the applicator tube is too rigid for affecting good distribution when the distal tip of the applicator is used as a manually employed wiping distributor. If the applicator is constructed of a very resilient or flexible plastic good distribution can be obtained but the structure of the applicable does not have sufficient structurally integrity.
The present invention combines the use of a relatively hard or relatively rigid plastic for the main or major portion of the applicator with a less rigid or resilient plastic for the distal end of the applicator.
In the best mode the plastic parts are extruded consecutively so that the major portion of the applicator is extruded followed by the extrusion of the minor part, that is, the distal end.
In the preferred embodiment of fabrication, the applicator of the present invention is injection molded. It is begun by first loading the mold to produce the major part of the applicator followed by injecting the more resilient portion. It is also considered that the reverse may be contemplated where the minor portion may first be injected into the mold followed by injecting the more rigid plastic major portion. The less rigid plastic may be of a foam plastic material, preferably of a closed cell nature.
The concept of producing composite articles is already well known and can be seen in such patents as U.S. Pat. Nos. 3,086,249; 3,115,682; 3,558,751; 3,341,043; 4,293,520; 4,507,258; 4,715,504; 4,990,301; 5,792,397; 5,897,822 and 6,062,841. These patents are incorporated herein in their entireties by reference.
It is contemplated that the plastic materials applicable are well known. The selection is predicated on the major portion being rigid and having integrity and the resilient part being sufficiently soft and flexible to assist in the spreading and distribution. Applicable polymers are PVC, hard/soft; polycarbonate, ABS; ABS/polycarbonate alloys, acrylic, nylon 6.6 and various rubbers.